The Twelfth Gordon Research Conference on Fertilization and the Activation of Development will provide a forum for presentation and discussion of new developments and ideas in this exciting, rapidly advancing field. This meeting will be held at the Holderness School, Plymouth, New Hampshire, July 25-July 30, 1997. This conference has been held every two years since 1974 and this will be the Silver Anniversary of the conference. It is the only Gordon Research Conference concerned with the interaction of the male and the female gametes in the vital process of fertilization and activation of the fertilized egg to begin the process of embryo formation. It provides a venue for the interaction of biochemists, cell biologists, molecular biologists, physiologists, geneticists and biophysicists working in the field. This conference has been singularly successful in fostering collaborations between widely disparate experience and seniority and between research laboratories in this country and in Europe, Japan, Australia and Latin America. These collaborations have born many fruitful results. There will be nine sessions in the conference, following the Gordon Research Conference format.. Seven of the sessions will have regular schedule speakers. 1) Sperm-zona pellucida Interactions; 2) Sperm capacitations and the acrosome reaction; 3) Genetic approaches to fertilization; 4) Molecules of sperm-egg plasma membrane binding and fusion; 5) Sperm-derived components of egg activation and embryo development; 6) Cell cycle events during egg maturation and after fertilization; 7) Early events of egg activation. An eight session will be a special session with talks chosen from posters and/or late breaking topics that will particularly feature junior scientists, including postdoctoral tellers and students. In addition we will have a key note speaker for the Tuesday evening session.